Intake air and carburetor heating arrangement for v-twin engines

ABSTRACT

A V-twin engine having a crankcase and a pair of cylinders defining a V-space therebetween, wherein the V-space is substantially enclosed, and a carburetor is positioned within the V-space. An intake air preheating arrangement supplies heated intake air to the carburetor, and a carburetor heating arrangement heats the V-space and the carburetor which is positioned within the V-space. Each of the foregoing arrangements, used separately or in combination within one another, aids in preventing “freeze-up” of the carburetor during running of the engine in a cold environment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/874,517, entitled INTAKE AIR AND CARBURETOR HEATING ARRANGEMENTS FORV-TWIN ENGINES, filed Oct. 18, 2007, which is a continuation of U.S.patent application Ser. No. 11/457,951, entitled INTAKE AIR ANDCARBURETOR HEATING ARRANGEMENT FOR V-TWIN ENGINES, filed Jul. 17, 2006,which is a division of U.S. patent application Ser. No. 10/813,202,entitled INTAKE AIR AND CARBURETOR HEATING ARRANGEMENTS FOR V-TWINENGINES, filed on Mar. 30, 2004, which claims the benefit under Title35, U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No.60/461,266, entitled INTAKE AIR AND CARBURETOR HEATING ARRANGEMENT FORV-TWIN ENGINES, filed on Apr. 8, 2003. The disclosure of the foregoingreferences are each hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to small internal combustion engines of the typecommonly used in lawn mowers, lawn and garden tractors, snow throwers,other working implements, or in sport vehicles. In particular, thepresent invention relates to heating the intake air and the carburetorsof such engines.

2. Description of the Related Art

Small internal combustion engines typically include a carburetor whichmixes ambient atmospheric air with liquid fuel to provide an air/fuelmixture for combustion within the engine. Usually, the intake air isdrawn from the atmosphere through an air filter to remove dirt and otherdebris from the intake air before the intake air enters the carburetor.A potential problem in such arrangements is that when the engine is usedin a cold environment, such as in a snow thrower application, the intakeair is often cold and moist, and may include snow. The moisture in thecold intake air may freeze and accumulate within the carburetor, causingthe carburetor to “freeze up” and inhibit good engine performance.

It is known to provide small single cylinder engines with ductarrangements which are disposed near the engine muffler. In operation,the duct is heated by radiant heat from the muffler during running ofthe engine. Air is drawn through the duct by the carburetor, and the airis heated before it enters the carburetor. However, such ducts aretypically formed from two or more separate components which fit togetherand cooperate to define the duct, and therefore, multiple parts arerequired.

A further problem in many small engines is that the carburetor itself isoften positioned in a manner in which it is exposed to the coldenvironment, potentially leading to carburetor “freeze up”. For example,the carburetor may be positioned on one side of the engine in such amanner that at least a portion of the body of the carburetor is disposedexternally of the engine enclosure structure and is exposed to theenvironment.

What is needed is an intake air and/or carburetor heating arrangementfor small internal combustion engines which is an improvement over theforegoing.

Also, intake air and/or carburetor heating arrangements which areadapted for use with V-twin engines are not known, thus, a further needis for an intake air and/or carburetor heating arrangement for a V-twinengine.

SUMMARY OF THE INVENTION

The present invention provides an apparatus and method for heating theintake air which is drawn into the carburetor of a V-twin engine, aswell as an apparatus and method for heating the carburetor of a V-twinengine.

In a V-twin engine having a crankcase and a pair of cylinders attachedto the crankcase and defining a V-space between the cylinders, a heaterbox is attached to one of the cylinders proximate the exhaust port ofthe cylinder. The heater box is connected to the air cleaner cavity ofthe engine via an insulated conduit. During operation of the engine,intake air is drawn from externally of the engine through an opening inthe cylinder wrap which surrounds the cylinder, and the air is heated asit passes near the exhaust port of the cylinder and into the heater box.Additionally, a portion of the cooling air from the flywheel/blower ofthe engine is directed between the cylinder and the cylinder wrap,around the exhaust port of the cylinder, and into the heater box. Theair which enters the heater box is heated within the heater box, andthen passes through the insulated conduit into the air cleaner cavityand thereafter into the carburetor. Thus, intake air, drawn from theforegoing two sources, is heated before it is drawn through thecarburetor and into the engine.

Additionally, a structure for heating the carburetor itself is provided.The carburetor is disposed in the V-space between the engine cylinders,and the V-space is substantially enclosed by the engine shroud, fueltank, and a wall portion of a duct structure. Air from the flywheel ofthe engine passes between a cylinder wrap and a cylinder of the engine,and through an opening in the cylinder wrap into the duct structure.Passage of the air through the opening in the duct structure creates asuction or “venturi effect” with which draws an additional portion ofheated air into the duct structure from an air space between the mufflerand the cylinder wrap. The heated air passes into the V-space to warmthe V-space, thus warming the carburetor which is positioned within theV-space.

Advantageously, the foregoing arrangement provides an apparatus andmethod for heating the intake air which is drawn into the engine toprevent “freeze-up” of the carburetor when the engine is used in a coldenvironment. Additionally, the foregoing arrangement provides anapparatus and method of heating the carburetor itself to further prevent“freeze-up” of the carburetor, in which warmed air is directed to asubstantially enclosed V-space between the engine cylinders in which thecarburetor is positioned.

In one form thereof, the present invention provides an internalcombustion engine, including a crankcase having a crankshaft rotatablydisposed therein; a blower driven by the crankshaft to generate an airstream; a pair of first and second cylinders connected to the crankcase;an air intake system in fluid communication with the cylinders; and anintake air heating arrangement, including a heater box disposedproximate the first cylinder, an interior of the heater box in airflowcommunication with the air stream; and a conduit in airflowcommunication with the heater box and with the air intake system,whereby air from the air stream is heated within the heater box and isconducted through the conduit into the intake system of the engine.

In another form thereof, the present invention provides a method ofheating intake air in an engine which includes a pair of cylindersdisposed at an angle with respect to one another to define a V-spacetherebetween, the method including the steps of generating an airstream; conducting the air stream proximate a hot portion of the engineto heat air within the air stream; capturing heated air from the airstream in a heater box; and conducting heated air from the heater box toan intake system of the engine.

In another form thereof, the present invention provides an internalcombustion engine, including a crankcase having a crankshaft rotatablydisposed therein; a blower driven by the crankshaft to generate an airstream; a pair of cylinders connected to the crankcase, the cylindersdisposed at an angle with respect to one another to define a V-spacetherebetween, the V-space substantially enclosed by portions of theengine; a carburetor disposed within the V-space; and a duct assemblydisposed proximate at least one of the cylinders and in airflowcommunication with the air stream and with the V-space, whereby air inthe air stream is heated within the duct assembly and is conducted tothe V-space to heat the carburetor.

In another form thereof, the present invention provides a method ofheating a carburetor of an engine having a pair of cylinders which aredisposed at an angle with respect to one another, the method includingthe steps of generating an air stream; conducting the air streamproximate a hot portion of the engine to heat air within the air stream;and conducting heated air from the air stream into a substantiallyenclosed V-space defined between the cylinders, in which the carburetoris positioned.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a front perspective view of a horizontal crankshaft, V-twinengine including intake air and carburetor heating arrangements inaccordance with the present invention;

FIG. 2 is a perspective cut-away view of a front portion of the engineof FIG. 1, showing the heater box, conduit, and air cleaner cavity ofthe intake air heating arrangement;

FIG. 3 is a fragmentary perspective view of an outside portion of one ofthe engine cylinders, showing the exhaust port, and the heater box ofthe intake air heating arrangement;

FIG. 4 is a fragmentary perspective view of an outside portion of one ofthe engine cylinders, shown with the cylinder wrap removed; and

FIG. 5 is a top schematic view of the engine of FIG. 1, looking directlydown one of the cylinders, showing the carburetor heating arrangement inaccordance with the present invention, wherein a portion of the aircleaner cavity is shown to the left of line L₁-L₁, and is disposed abovethe flywheel/blower of the engine.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrates preferred embodiments of the invention, and suchexemplifications are not to be construed as limiting the scope of theinvention any manner.

DETAILED DESCRIPTION

Referring first to FIG. 1, a small internal combustion engine 20 isshown as a horizontal crankshaft V-twin engine, such as the engine whichis described in detail in U.S. patent application Ser. No. 10/409,262,entitled INTERNAL COMBUSTION ENGINE, filed on Apr. 8, 2003 (AttorneyFile Ref.: TEL0633-02), assigned to the assignee of the presentinvention, the disclosure of which is expressly incorporated herein byreference. Although engine 20 is shown as a horizontal crankshaft V-twinengine which may advantageously be used in a snow thrower, for example,the carburetor and intake air heating concepts of the present inventionalso could be embodied in vertical crankshaft V-twin engines.

Engine 20 generally includes crankcase 22 having a pair of enginecylinders 24 mounted to crankcase 22 in the manner described in theabove-incorporated U.S. patent application Ser. No. 10/409,262. Ahorizontally disposed crankshaft 26 is rotatably carried withincrankcase 22, and is coupled to a pair of conventional piston/connectingrod assemblies (not shown), one corresponding to each engine cylinder.Engine 20 also includes intake air heating arrangement 28 and carburetorheating arrangement 30, which are discussed in detail below.

Engine cover or shroud 32 is connected to crankcase 22, and covers atleast a portion of each of crankcase 22 and cylinders 24. Shroud 32 maybe formed of metal, or from an injection molded or vacuum-formed plasticmaterial, for example. Cylinder wraps 34, typically made of a relativelythin sheet metal, are also connected to crankcase 22 and cylinders 24,and closely surround cylinders 24 for directing cooling air aroundcylinders 24 as discussed below. Fuel tank 36 is mounted via brackets 38to the upper ends of cylinder wraps 34. Air inlet screen 40 is mountedto shroud 32, and covers an opening in shroud 32 through which intakeair is drawn during running of engine 20 by rotation of flywheel/blower42 (FIG. 5), which is attached to an end of crankshaft 26 which extendsexternally of crankcase 22, and includes a plurality of fins 43.Specifically, rotation of flywheel/blower 42 draws intake air throughlouvers 44 in air inlet screen 40 and into an area defined betweencrankcase 22 and shroud 32.

Referring to FIGS. 2 and 5, cylinders 24 are disposed at an angle withrespect to one another to define V-space 46 therebetween. Typically,cylinders 24 are disposed at a 90° angle with respect to one another.Shroud 32 closes the front side of V-space between cylinders 24, andincludes air cleaner cavity 48 which optionally includes an air cleanerelement 50 therein. Further details regarding intake air cleaner cavity48 and air cleaner element 50 are discussed in U.S. patent applicationSer. No. 10/408,882, entitled AIR CLEANER ASSEMBLY FOR INTERNALCOMBUSTION ENGINES, filed on Apr. 8, 2003 (Attorney File Ref.: TEL0681),assigned to the assignee of the present invention, the disclosure ofwhich is expressly incorporated herein by reference.

In FIG. 5, engine 20 is shown from a top view, with engine 20 rotatedclockwise about 45° such that the left cylinder 24 in FIG. 5 is disposedvertically and the right cylinder in FIG. 5 is disposed horizontally. Aportion of air cleaner cavity 48 and air cleaner element 50 are shown tothe left of line L₁-L₁ of FIG. 5, which are disposed aboveflywheel/blower 42 and air inlet screen 40. To the right of line L₁-L₁in FIG. 5, air cleaner cavity 48 and air cleaner element 50 are omittedand flywheel/blower 42 is shown, which is disposed beneath air cleanercavity 48 and air cleaner element 50, and a portion of air inlet screen40 is cut away to show pulley 51 of the recoil starter assembly ofengine 20.

As shown in FIG. 5, carburetor 52 is disposed within V-space 46.Carburetor 52 is connected to shroud 32 and includes carburetor body 54and fuel bowl 56. Throat 58 is disposed through carburetor body 54 andincludes an inlet end in communication with air cleaner cavity 48. Chokevalve 60 and throttle valve 62 are rotatably disposed within throat 58of carburetor 52 on opposite sides of venturi region 64 of throat 58.Fuel bowl 56 includes a quantity of fuel which is drawn upwardly intothroat 58 during running of engine 20 for mixing with intake air atventuri region 64. Outlet end 66 of carburetor 52 is connected to intakemanifold 68, which includes a pair of intake pipes 70, each connected toa respective intake port 72 of cylinders 24. Intake manifold 68, intakepipes 70, and intake ports 72 of cylinders 24 are all disposed withinV-space 46. Although engine 20 is described herein as including acarburetor 52, the intake air heating arrangement of the presentinvention could also be used to heat the intake air of an engine whichincludes a fuel injection system.

Exhaust ports 74 of cylinders 24 are disposed on a side of cylinders 24opposite intake ports 72, and face outwardly of V-space 46. Thus, heatfrom exhaust ports 74 is readily dispersed outwardly of engine 20 to thesides of engine 20.

Referring to FIGS. 2-4, intake air heating arrangement 28 will now bedescribed. Heater box 80 is connected to one of cylinders 24 proximateexhaust port 74 of the cylinder 24. Heater box 80 may be formed of asuitable metal, such as sheet metal or stainless steel, for example.Heater box 80 generally includes inlet 82 (FIGS. 3 and 4), and outlet 84which is shown in FIG. 2 in the form of a cylindrical coupling.

Air cleaner cavity 48 of shroud 32 includes an inlet opening 86 formedin a wall thereof. Inlet opening 86 may be formed as a knock-out portionwithin the wall of air cleaner cavity 48, in which the knock-out portionis removed from the wall of air cleaner cavity 48 during assembly ofengine 20 if engine 20 is to be equipped with air heating arrangement28. Alternatively, if engine 20 is not to be equipped with air heatingarrangement 28, the knock-out portion may be left in place. Conduit 88includes first end 90 connected to outlet 84 of heater box 80, andsecond end 92 connected to inlet opening 86 of air cleaner cavity 48 tothereby fluidly communicate heater box 80 with air cleaner cavity 48.Conduit 88 is made of a flexible material such as rubber, which materialis also resistant to heat transfer such that conduit 88 is insulated, asdiscussed further below. Alternatively, the construction of conduit 88may vary. For example, conduit 88 may be a passage integrally formedwithin shroud 32, or may take the form of a separate duct piece attachedto shroud 32 and defining a passage between the duct member and shroud32.

Referring to FIGS. 3 and 4, exhaust port 74 of cylinder 24 includes anexhaust pipe/adapter 94 mounted to exhaust port 74 by suitable fasteners95. As is clearly shown in FIG. 4, adapter 94 includes first flange 96mounted to exhaust port 74 of cylinder 24 via fasteners 95 with a wallof heater box 80 secured between flange 96 and exhaust port 74, and anopposite second flange 98 to which muffler 100 (FIGS. 1 and 5) may beattached. Cylinder wrap 34 surrounds cylinder 24 and is positionedclosely adjacent cooling fins 102 of cylinder 24. In FIG. 4, cylinderwrap 34 has been removed for clarity. Referring to FIG. 3, cylinder wrap34 includes an opening 104 through which exhaust outlet adapter 94extends, with opening 104 having a larger diameter than exhaust outletadapter 94 to define a gap 106 between opening 104 and exhaust outletadapter 94.

As shown in FIGS. 3 and 4, the space between cylinder wrap 34 and theouter wall of cylinder 24 defines an air passage 108, through which airis directed by the rotating of flywheel/blower 42 during running ofengine 20. Air passes along arrows A₁ through air passage 108, wheresame is heated by radiant heat from cylinder 24 and from exhaust port 74and adapter 94 before entering inlet 82 of heater box 80. Additionally,as shown in FIG. 3, air is drawn by the passage of air along arrows A₁in the direction of arrows A₂ from externally of engine 20 through gap106 between opening 104 in cylinder wrap 34 and exhaust port adapter 94.The air corresponding to arrows A₂ is heated from exhaust port adapter94 and muffler 100 before entering inlet 82 of heater box 80. In thismanner, heated air enters heater box 80 from the foregoing two sourcesalong arrows A₁ and A₂. Further, heater box 80 is itself heated byconduction from cylinder 24 during running of engine 20, such that airwithin heater box 80 is further heated.

Referring to FIG. 2, air within heater box 80 passes through conduit 88into air cleaner cavity 48. Conduit 88 is made of an insulating materialto prevent loss of heat from the air therewithin to the outside ofengine 20, such that the air within conduit 88 retains its heat as samepasses from heater box 80 into air cleaner cavity 48. Heated air withinair cleaner cavity 48 then passes through filter element 50 (FIG. 5) toremove particulate matter from the air. Alternatively, air cleanercavity 48 may lack filter element 50. The heated air thereafter passesinto the inlet end of carburetor 52, as shown in FIG. 5, for mixing withfuel at venturi region 64 of throat 58 to provide an air/fuel mixturefor combustion within engine 20. In this manner, the intake air ofengine 20 is heated before same enters carburetor 52, preventing“freeze-up” of carburetor 52. Also, if desired, engine 20 may include apair of heater boxes 80, one connected to each cylinder 24, and a pairof conduits for directing air from the heater boxes into air cleanercavity 48.

Referring to FIG. 5, carburetor heating arrangement 30 will now bedescribed. Duct assembly 120 generally includes duct 122, wall 124, andcylinder wrap 34. Wall 124 of duct assembly 120 is connected to bothcylinders 24 to substantially enclose the rear side of V-space 46 whichis disposed opposite shroud 32. Additionally, fuel tank 36, shown inphantom lines in FIG. 5, is connected via brackets 38, as shown in FIG.1, to the upper portions of cylinders 24. In this manner, shroud 32,wall 124, and fuel tank 36 cooperate to substantially enclose V-space 46between cylinders 24, such that airflow into and out of V-space 46 iscontrolled in the manner set forth below.

Cylinder wrap 34 includes an outlet 126 in the form of a section ofcylinder wrap 34 which is separated from the remainder of cylinder wrap34, and which opens into duct 122. Duct 122 includes a first end 128 incommunication with air space 130 between muffler 100 and cylinder wrap34, and a second end 132 in communication with V-space 46.

In operation, air is directed from flywheel/blower 42 between cylinderwrap 34 and cylinder 24 along arrows A₃, and is heated from cylinder 24A portion of this heated air passes through outlet 126 of cylinder wrap34 into duct 122 along the direction of arrow A₄. The forced passage ofair through outlet 126 creates a low pressure area within duct 122behind outlet 126, i.e., a “venturi” effect, at first end 128 of duct122, thereby drawing additional heated air from air space 130 throughduct 122 along arrow A₅. Heated air from air space 130 combines with theheated air passing through outlet 126 of cylinder wrap 34, and thiscombined heated air passes through duct 122 along arrow A₆ to second end132 of duct 122 and is discharged into V-space 46. In this manner, thesubstantially enclosed V-space 46 is heated by a continuous input ofheated air into V-space. Heating of V-space 46 in turn heats carburetor52, which is positioned within V-space 46. Heating of carburetor 52 aidsin preventing “freeze-up” of carburetor 52 during running of engine 20.

After heating carburetor 52, spent heating air within V-space 46 mayexit V-space 46 by passing through openings within V-space 46, such asgaps between fuel tank 36 and shroud 32 or between fuel tank 36 and wall124 of duct 122, for example. Alternatively, a dedicated duct structureor conduit (not shown) may be used to vent the spent heading air fromV-space 46.

Advantageously therefor, intake air preheating arrangement 28, includingheater box 80 and conduit 88, supplies heated intake air to carburetor52, and carburetor heating arrangement 30 heats V-space 46 andcarburetor 52 which is positioned within V-space. Each of the foregoingarrangements, used separately or in combination with one another, aidsin preventing “freeze-up” of carburetor 52 during running of engine 20in a cold environment.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1-19. (canceled)
 20. An internal combustion engine, comprising: acrankcase having a crankshaft rotatably disposed therein; a blowerdriven by said crankshaft to generate an air stream; at least onecylinder connected to said crankcase, said cylinder including an exhaustport and an exhaust pipe connected to said exhaust port; an air intakesystem in fluid communication with said cylinder; and an intake airheating arrangement, comprising: a heater box disposed proximate saidcylinder, at least a portion of said heater box secured between saidexhaust port and said exhaust pipe, an interior of said heater box inairflow communication with said air stream and with said air intakesystem, whereby air from said air stream is heated within said heaterbox and is conducted into said intake system of said engine.
 21. Theengine of claim 20, wherein said heater box includes at least one wallformed as a relatively thin metal sheet, said metal sheet securedbetween said exhaust port and said exhaust pipe.
 22. The engine of claim20, wherein said exhaust pipe includes a mount flange, said mount flangeconnected to said exhaust port by a least a pair of fasteners with atleast a portion of said heater box secured between said mount flange andsaid exhaust port.
 23. The engine of claim 20, wherein said intake airheating arrangement further includes a conduit in airflow communicationwith said heater box and with said air intake system.
 24. The engine ofclaim 20, wherein said air intake system further includes an aircleaner, said air cleaner connected to said carburetor and in airflowcommunication with said conduit.
 25. The engine of claim 20, furthercomprising a muffler in exhaust flow communication with said cylinderand disposed proximate said heater box, whereby air from said air streamis heated within said heater box by heat from said muffler.
 26. Theengine of claim 25, wherein said heater box further includes anauxiliary inlet in fluid communication with a space proximate saidmuffler, and a venturi portion disposed proximate said auxiliary inlet,whereby passage of the air stream through said venturi portion lowersthe pressure of the air stream to draw heated air from said spaceproximate said muffler through said auxiliary inlet and into the airstream.
 27. The engine of claim 20, further comprising a cylinder wrapat least partially enclosing said cylinder, said cylinder and saidcylinder wrap defining an air passage in airflow communication with saidheater box through which said air stream is conducted.
 28. The engine ofclaim 20, wherein said crankshaft is disposed horizontally.